Active matrix substrate and method of manufacturing the same

ABSTRACT

A method of manufacturing an active matrix substrate comprises forming a plurality of elements on an element formation substrate, forming wirings on a final substrate, transferring some elements selected from the elements, and selectively connecting some elements to the wirings on the final substrate. According to this method, it is possible to manufacture an active matrix substrate providing a high definition image on a large substrate or a non-glass substrate, at a low cost.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 11-179214, filed Jun. 25,1999, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an active matrix substrate for a liquidcrystal display device and a method of manufacturing the same.

Liquid crystal display devices (LCD) are advantageous since they areformed thin and display color images with low power consumption. Byvirtue of these advantages, the LCDs are widely used for lap-toppersonal computers. The image quality of the LCDs is good enough to beemployed not only for electric-data display devices but also for TVscreens.

Of the LCD devices, an active matrix type LCD is used as a flat paneldisplay capable of providing full-color images with a high quality. Theactive matrix type LCD is formed of a first glass substrate, a secondglass substrate and liquid crystal which is injected between the firstand the second glass substrate. In the first glass substrate, thintransistors (TFT), which employ amorphous silicon or poly crystallinesilicon as an active layer, are arranged in a matrix form. The secondglass substrate is fixed so as to face the first glass substrate with agap of about 5 μm interposed between them.

FIG. 1 shows a cross-sectional view of a pixel portion of a conventionalactive matrix type LCD.

A scanning line 3502 and a storage capacitor line 3503 are formed on aglass substrate 3501. A gate insulating film 3504 is formed over thelines 3502 and 3503. Furthermore, a pixel electrode 3505 is selectivelyformed on the gate insulating film 3504.

Reference numeral 3506 is a TFT portion, which is formed of asemiconductor layer 3507, a channel protecting insulating film 3508formed on the semiconductor layer 3507, and two doped semiconductorlayers 3509 facing each other. The two doped semiconductor layers areformed in contact with the semiconductor layer 3507 while an end portionof each of the doped semiconductor layers is mounted on the channelprotecting insulating film 3508. A source electrode 3510 and a drainelectrode 3511 are formed respectively on the two doped semiconductorlayers 3509. The source electrode 3510 is connected to a signal line(not shown). The drain electrode 3511 is connected to the pixelelectrode 3505. A protective insulating film 3512 is formed over the TFTportion 3506.

With recent technical development, a field of view has been widened.Accordingly, a narrow viewing angle of the LCD has been overcome. Inaddition to this, since the TFT array can be formed on the glasssubstrate, a relatively large display having a diagonal length of about10 to 25 inches has been realized.

However, to realize a high definition TV (HDTV), a large screen having adiagonal length of about 40-60 inches is desired. To manufacture the TFTarray for such a large screen, it is necessary to construct an assemblyline capable of holding an ultra-large glass substrate larger than 1 msquare. A large equipment cost is inevitably required.

A method of making the large screen by jointing a plurality ofsubstrates carrying TFT arrays is disclosed in Japanese PatentApplicaltion KOKAI publication No. 10-268332. However, this method hasthe following problems. Since the substrates are not jointed accurately,an aperture ratio of the joint portion is low. It is difficult toaccurately control the level of the joint portion between thesubstrates, taking the thickness (5 μm) of the liquid crystal layer intoconsideration. Therefore, a large quantity of the substrates are notmanufactured.

On the other hand, a mobile data terminal equipment providing electronicdata anytime and anywhere was developed by making use of “low powerconsumption” of the LCD. The mobile data terminal equipment has beenused in a wide variety of fields. In future, it is expected thatelectronic data will be displayed with the same ultra precision as thatof printing matter, that is, about 150-300 pixel/inch (ppi).

These mobile data terminal equipments have to be formed light with a lowpower consumption. When a liquid crystal display is formed on an A4-sizeglass substrate of about 0.7 mm-thick, the total weight of the displayresults in 220 g. If the weight of the bezel for fixing the display isincluded, the total weight of the device will be about 400 g or more.

The weight of the display device can be reduced by about ½ if a plasticsubstrate is employed. The weight can be further reduced, if a filmsubstrate is used. Such a display device is suitable for use in themobile data terminal equipment. In these circumstances, attempts havebeen made to form the TFTs on the plastic substrate or the filmsubstrate. When the TFTs are formed on these substrates, however, it isnecessary to reduce the processing temperature. If the TFTs are formedat a low processing temperature, performance of the TFTs may bedegraded, with the result that limitations may be imposed on imagequality and the number of pixels. Furthermore, the thermal expansioncoefficiency of these substrates is high and plastic deformation occursat a low temperature. For these reasons, it is conceivable that the highdefinition display device may not be attained.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an active matrixsubstrate for achieving the formation of a high definition image at alow cost even if a large substrate or a non-glass substrate is used, andalso provide a method for manufacturing the same.

According to a first aspect of the present invention, to attain theaforementioned objects, there is provided a method of manufacturing anactive matrix substrate comprising:

a first step of forming a plurality of elements on a first substrate;

a second step of forming wirings on a second substrate;

a third step of transferring some elements selected from the pluralityof elements onto the second substrate from the first substrate; and

a fourth step of selectively connecting the some elements transferredonto the second substrate to the wirings.

According to a second aspect of the present invention, there is provideda method of manufacturing an active matrix substrate comprising:

a first step of forming a plurality of elements on a first substrate;

a second step of transferring some elements selected from the pluralityof elements onto a second substrate from the first substrate;

a third step of forming wirings on the second substrate after the secondstep; and

a fourth step of selectively connecting the some elements and thewirings.

In the methods of manufacturing an active matrix substrate according tothe first and second aspects, it is preferable that the following stepsbe carried out.

The third step includes the steps of:

adhering the plurality of elements formed on the first substrate ontothe third substrate;

etching away the first substrate; and

transferring the some elements selected from the plurality of elementsadhered on the third substrate to the second substrate.

The third step includes the steps of:

forming an adhesion layer on the third substrate;

transferring the plurality of elements formed on the first substrateonto the third substrate via the adhesion layer; and

selectively heating portions of the adhesion layer on which the someelements are formed, to thereby transfer the some elements from thethird substrate to the second substrate.

In the aforementioned step, the elements may be removed from the elementformation substrate by laser irradiation in place of heat application.Alternatively, the elements formed on the element formation substratemay be transferred on the adhesion layer which is heated and furthertransferred from the intermediate transfer substrate to the finalsubstrate by UV irradiation.

The third step includes a step of selecting the some elements such thata largest interval of two adjacent elements arbitrarily chosen from thesome elements is larger than a largest interval of two adjacent elementsarbitrarily chosen from the plurality of elements formed on the firstsubstrate.

The third step includes a step of selecting the some elements atpredetermined intervals thereamong, and a step of repeating the step ofselecting the some elements.

The first step includes the steps of:

forming an underlying layer on the first substrate;

forming the plurality of elements on the underlying layer; and

forming a protective layer individually on each of the plurality ofelements, such that the plurality of elements are covered with theunderlying layer and the protective layer.

The method of the present invention further comprises a step ofseparating the underlying layer into sections such that the underlyinglayer remains only just under each of the plurality of elements.

Note that the underlying layer is desirably a stacked layered composedof an etching stopper layer formed on the first substrate and anundercoat layer formed on the etching stopper layer.

According to a third aspect of the present invention, there is provideda method of manufacturing an active matrix substrate comprising:

a first step of forming an underlying layer on a first substrate;

a second step of forming a plurality of circuit units, on the underlyinglayer, composed of at least one element and at least one wiringconnected to the at least one element;

a third step of adhering the plurality of circuit units formed on thefirst substrate to a third substrate via an adhesion layer formed on thethird substrate;

a fourth step of etching away the first substrate; and

a fifth step of selectively transferring the plurality of circuit unitsadhered onto the third substrate to the second substrate.

The method of manufacturing an active matrix substrate according to thethird aspect of the present invention may be carried out as follows.

The fifth step includes a step of selectively heating portions of theadhesion layer on which some circuit units to be transferred are formed,to thereby transfer the circuit units from the third substrate to thesecond substrate.

The second step includes a step of forming a protective layerindividually on each of the plurality of circuit units, such that theplurality of circuit units are covered with the underlying layer and theprotective layer.

The method according to a third aspect of the present invention furthercomprises a step of separating the underlying layer into sections suchthat the underlying layer remains only just under each of the pluralityof circuit units.

The first step includes a step of forming a stacked-layer film composedof an etching stopper layer on the first substrate and an undercoatlayer formed on the etching stopper layer.

Each of the plurality of circuit units includes a plurality of pixelelectrodes, and the fifth step is repeated a plurality of times suchthat an interval between adjacent electrodes of the plurality of pixelelectrodes is kept substantially constant through the plurality ofcircuit units transferred.

According to a fourth aspect of the present invention, there is providedan active matrix substrate comprising:

a substrate;

an adhesion layer formed on the substrate;

an undercoat layer formed on the adhesion layer

a plurality of elements formed on the undercoat layer;

wherein the adhesion layer and the undercoat layer are separated suchthat the adhesion layer and the undercoat layer remain only just undereach of the plurality of elements.

A substrate formation substrate for use in manufacturing the activematrix substrate comprises:

a substrate;

an exfoliation layer formed on the substrate for being removed by heatapplication; and

elements formed on the exfoliation layer at the same height, theelements being electrically isolated from each other.

An intermediate transfer substrate for use in manufacturing the activematrix substrate comprises:

a substrate;

an exfoliation layer formed on the substrate for being removed by heatapplication;

elements formed on the exfoliation layer at the same height, theelements being electrically isolated from each other.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a cross-sectional view of a pixel portion of a conventionalactive matrix type LCD;

FIG. 2 is a partial plan view of an active matrix substrate according toa first embodiment of the present invention;

FIG. 3 is an enlarged view of a TFT portion of FIG. 2;

FIG. 4 is a cross-sectional view taken along the line 4—4 of FIG. 3;

FIG. 5A is a cross sectional view of the TFT portion formed on anelement formation substrate according to the first embodiment;

FIGS. 5B and 5C are modified examples of FIG. 5A;

FIGS. 6 to 10 are cross-sectional views sequentially showing stepsstarting from formation of elements to formation of an intermediatetransfer substrate, in a method of manufacturing an active matrixsubstrate according to the first embodiment of the present invention.

FIGS. 11 to 15 are cross-sectional views sequentially showing steps offorming wiring on a final transfer substrate in the method of the firstembodiment of the present invention;

FIGS. 16 to 19 are cross sectional views sequentially showing steps oftransferring an element to the final transfer substrate in the method ofthe first embodiment of the present invention;

FIGS. 20A to 24B are plan views subsequently showing steps oftransferring a plurality of elements from the intermediate transfersubstrate to the final transfer substrate, in one operation, in themethod of the first embodiment of the present invention;

FIG. 25 is a cross sectional view of a liquid crystal display deviceusing the active matrix substrate according to the first embodiment ofthe present invention;

FIGS. 26 to 31 are cross sectional views sequentially showing a methodof manufacturing an active matrix substrate according to a secondembodiment of the present invention;

FIG. 32 is a plan view of the active matrix substrate for explaining amethod of manufacturing the active matrix substrate by using two elementformation substrates in the second embodiment;

FIG. 33 is a cross-sectional view of a substrate taking along the line33—33 of FIG. 32;

FIG. 34 is a plan view of the active matrix substrate for explaininganother method of forming the active matrix substrate by using twoelement formation substrates in the second embodiment;

FIG. 35 is a cross-sectional view taken along the line 35—35 of FIG. 34;

FIG. 36 is a cross-sectional view of the active matrix substrate forexplaining a method of forming wiring on a final transfer substrateafter the TFT element is transferred, according to a third embodiment ofthe present invention;

FIG. 37 is a partial plan view of the final transfer substrate accordingto the third embodiment (FIG. 36 corresponds to a cross sectional viewtaken along the line 36—36 of FIG. 37);

FIG. 38 is a cross-sectional view of a modified example of the thirdembodiment;

FIG. 39 is a partial plan view of the final transfer substrate accordingthe modified example of the third embodiment (FIG. 38 is across-sectional view taken along the line 38—38 of FIG. 39);

FIG. 40 is a partial cross-sectional view of a substrate for explaininga method of forming a micro-capsule liquid crystal display device on anelement formation substrate, in a fourth embodiment of the presentinvention; and

FIG. 41 is a cross-sectional view of a substrate for explaining a methodof forming a micro-capsule liquid crystal display device transferred ona final transfer substrate in the fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Now, embodiments of the present invention will be explained withreference to the accompanying drawings.

First Embodiment

In the first embodiment, an active matrix substrate is formed by formingan amorphous silicon TFT (hereinafter, simply referred to as “TFT”) onan element formation substrate (first substrate), transferring the TFTonto an intermediate transfer substrate (third substrate), andthereafter transferring the TFT to a final transfer substrate (secondsubstrate) having wiring formed thereon.

A plan view of an entire active matrix substrate 101 of this embodimentis shown in FIG. 2. A single TFT portion of FIG. 2 is enlarged in FIG.3. A cross-sectional view taken along the line 4—4 of FIG. 3 is shown inFIG. 4.

Now, the structure of the active matrix substrate 101 of this embodimentwill be explained with reference to FIG. 4. Note that details of the TFTportion shown in FIG. 3 are omitted in FIG. 2. As shown in FIG. 2, aplurality of pixels are arranged on the active matrix substrate 101 likean array. In each pixel, a TFT 102 and a pixel electrode 103 areprovided. Each TFT 102 is connected to the pixel electrode 103, a signalline 104, and a scanning line 105.

FIG. 4 shows each pixel. The scanning line 105 is formed on a finaltransfer substrate 301 made of glass. Further, an interlayer insulatinglayer 302, the signal line 104, and a flattening layer 303 are stackedon the final transfer substrate 301. The TFT 102 is formed on theresultant structure by successively stacking an adhesion layer 304, anundercoat layer 305, a gate electrode 306, a gate insulating layer 307,a semiconductor layer 308, and a channel protecting insulating layer309. Further on this structure, two n-type semiconductor layers 310 areformed so as to cover an upper portion of a channel protectinginsulating layer 309. The two n-type semiconductor layers 310 are alsoconnected to the semiconductor layer 308. A source electrode 311 and adrain electrode 312 are formed respectively on the two n-typesemiconductor layers 310. Further on the layer 310, a passivation layer313 is formed. A contact hole 314 is formed in the portions of thepassivation layers 313 on the source electrode 311 and the drainelectrode 312. The pixel electrode 103 is formed on the flattening layer303 in contact with the drain electrode 312.

As shown in FIG. 3, a contact portion 201 is formed in each of thescanning line 105 and the gate electrode 306. The scanning line 105 andthe gate electrode 306 are connected by way of a connecting wiringelement 202. The signal line 104 is connected to the source electrode311 of the TFT 102 by way of the contact portion 201, the connectingelectrode 203, and the contact hole 314.

A storage capacitor line 204 may be provided in the pixel electrode 103as shown in FIG. 3. The storage capacitor line 204 is responsible notonly for retaining voltage of the pixel electrode 305 but alsopreventing a capacitive coupling noise, which is induced by ascanning-line pulse and applied to the liquid crystal, from beingdependent upon a signal voltage. The storage capacitor line 204 isformed in the same layer of the signal line 104 and in parallel to thesignal line 104, in FIG. 3. In another case considering the apertureratio and the like, the storage capacitor line 204 may be formed in thesame layer of the scanning line 105 and in parallel to the scanning line105. This is effective for improving the aperture ratio with respect tothe lengthwise pixel. Alternatively, the storage capacitor may be formedon the scanning line dedicated to the just previous pixel in thescanning direction, with the electrode thereof over lapping thereon. Inthis case, the storage capacitor line is assumed to be the just previousscanning line. The storage capacitor line 204 is connected to a powersupply source (not shown), from which an appropriate voltage may beapplied to the storage capacitor line 204.

Now, a method of forming the TFT 102 on the element formation substrate401 will be first explained with reference to FIG. 5A.

An etching stopper layer 402 is formed on an element formation substrate401 made of glass. The etching stopper layer 402 serves as an etchingstopper against a hydrofluoric-acid-based etchant in a glass etchingstep performed later. A metal oxide film such as a tantalum oxide filmor a nitride film is usually used as the etching stopper layer 402.

Then, on the resultant structure, an undercoat layer 305 of a siliconoxide film or silicon nitride film is formed. Furthermore, the gateelectrode 306 is formed of MoTa or MoW on the undercoat layer 305.Thereafter, a gate insulating layer 307 is formed on the gate electrode306 in a thickness of about 400 nm by depositing a silicon nitride filmin accordance with a plasma CVD method so as to cover it. The gateinsulating layer 307 may be a stacked film of a silicon nitride film anda silicon oxide film.

An amorphous silicon layer serving as a semiconductor layer 308 isformed in a thickness of about 50 nm. Subsequently, a silicon nitridefilm serving as a channel protecting insulating layer 309 is formed-in athickness of about 100-400 nm. Thereafter, a channel protectinginsulating layer 309 is formed above the gate electrode 306 inself-alignment therewith by light exposure applied from a rear surfaceof the substrate.

Then, a phosphorus-doped n-type semiconductor layer 310 is formed byCVD, followed by etching the n-type semiconductor layer 310 and thesemiconductor layer 308 each to be an island shape. Subsequently, thesource electrode 311 and the drain electrode 312 are formed on then-type semiconductor layer 310. The n-type semiconductor layer 310 ispatterned to selectively remove the n-type semiconductor layer 310 onthe channel protecting insulating layer 309 using the source electrode311 and the drain electrode 312 as a mask. Furthermore, the passivationlayer 313 is formed of a silicon nitride film by plasma CVD. A contacthole 314 is selectively formed in the paissivation layer just above thesource electrode 311 and the drain electrode 312. The height of the TFT102 from the undercoat layer 305 to the passivation layer 313 is set atabout 500 nm to 2 μm.

Note that the passivation layer 313 may be formed after etching of thegate insulating layer 307 or the undercoat layer 305 for separating theelement to be transferred (described later), as shown in FIGS. 5B or 5C.This enables the passivation film 313 to cover the sides of the gateinsulating film 307, with the result that the reliability of the TFT andthe LCD is enhanced.

Now, a method of transferring the TFT from the element formationsubstrate 401 to an intermediate transfer substrate 701 will beexplained with reference to FIGS. 6 to 10. Note that a detailedstructure of the TFT element is omitted from FIGS. 6 to 10.

As shown in FIG. 6, the etching stopper layer 402, the undercoat layer305, and TFTs 102 are formed on the element formation substrate 401.Each of TFTs 102 is individually covered with a protective layer 601 asshown in FIG. 7. As the protective layer 601, a rubber-base negativeresist is used in this embodiment. However, use may be made of anorganic resin or the like having a heat resistance and a mechanicalstrength. The protective layer 601 is formed larger than TFT 102horizontally and vertically by about 2-40 μm (as shown by a broken linein FIG. 5) so as to cover the entire TFT 102.

Thereafter, dry-etching is performed to remove the portions of theetching stopper layer 402 and the undercoat layer 305 not covered withthe protective layer 601. The etching stopper layer 402 and theundercoat layer 305 formed under TFTs are separated from each other.

Now, as shown in FIG. 8, light absorbers 702 are formed on anintermediate transfer substrate 701 made of transparent glass at thepositions corresponding to individual TFTs 102. Then, anadhesion/exfoliation layer 703 is formed over all light absorbers 702.The light absorber 702 is formed of a metal film such as, MoTa, MoW orthe like. The light absorber 702 is blackened at a surface facing theintermediate transfer substrate 701. The light absorber 702 preferablyhas a good heat conductivity. When heat is applied, theadhesion/exfoliation layer 703 is reduced in viscosity, losingadhesiveness. As the adhesion/exfoliation layer 703, a wax such asApeazon wax (manufactured by Apeazon Product Limited) may be used.Alternatively, a material which develops foams by heat application andloses its adhesiveness, for example, Riba-alpha (manufactured by NittoDenko corporation), may be used. It is preferable that the intermediatetransfer substrate 701 should have the same thermal expansioncoefficient as the element formation substrate 401.

The light absorbers 702 are aligned with the corresponding protectivelayers 601 of the TFTs 102. As a result, the structure shown in FIG. 9is obtained, in which the adhesion/exfoliation layer 703 is in contactwith the protective layers 601.

After the peripheral side surface of the intermediate transfer substrate701 is protected with a tape or the like, the element formationsubstrate 401 is etched with a solution mixture of hydrofluoric acid anda surfactant. The etching is controlled so as to stop by the etchingstopper layer 402.

The etching may be performed by a mechanical etching method to asubstantial amount, followed by a chemical etching method. It ispreferable to adopt a uniformly-etchable chemical etching method toenhance etching selectivity of the etching stopper layer 402.

Alternatively, a stacked layer of an amorphous silicon film and asilicon nitride film may be used in place of the etching stopper layer402. In this case, a material easily causing a laser ablation is formedunder the stacked layer, and then, a laser light is applied through theelement formation substrate 401. In this manner, the TFT 102 isseparated. As the material easily causing a laser ablation, use may bemade of hydrogenated amorphous silicon, an insulating film containing agas such as a silicon nitride film formed at a low temperature, andpolyamide having imide at a low rate. In this manner, the TFT 102 may betransferred to the intermediate transfer substrate 701 as shown in FIG.10.

Next, a method of forming wirings of a final transfer substrate 301 willbe explained with reference to FIGS. 11 to 15.

As the material for the final transfer substrate 301, a glass substratesuch as no-alkali glass or soda-lime glass, or a plastic substrate, maybe used. A no-alkali glass substrate is used in this embodiment.

First, as shown in FIG. 11, a scanning line 105 of about 1-5 μm thickand 30 μm wide is formed by applying a conductive resin paste on thefinal transfer substrate 301 in accordance with screen printing, forminga pattern, and annealing at about 450-600° C. Alternatively, thescanning line 105 may be formed by attaching a photosensitive conductivefilm such as Fodel etc.(made of Du Pont-Mitsui Polychemicals companyLtd.) and forming a pattern by exposing the photosensitive conductivefilm to light through a photomask. As a further alternative method, thescanning line 105 may be formed by forming a thin film in accordancewith a deposition or sputtering method, subjecting the resultant film tolight exposure with a resist as a mask, and applying etching to thefilm.

Then, an interlayer insulating layer 302 is formed on the resultantstructure, as shown in FIG. 12. The interlayer insulating layer 302 isformed by stacking two layers of silicon oxide films containingphosphorus, each being formed by coating the silicon oxide and bakingthe coated film at about 600° C. As mentioned above, if an additive isdoped in the silicon oxide film and the silicon oxide film is subjectedto reflowing at a low temperature, the resultant interlayer insulatingfilm 302 is formed with few number of pin holes. The interlayerinsulating layer 302 may be formed of an inorganic film, polyimide,acrylic resin, benzocyclobutene (BCB), or the like.

A signal line 104 is formed on the interlayer insulating layer 302 in awidth of about 30 μm and a thickness of about 1-3 μm by using the samematerial and in the same manner as in the scanning line 105, as shown inFIG. 13. A flattening layer 303 is then formed on the signal line 104,as shown in FIG. 14. The flattening layer 303 is formed by applying anacrylic resin in a thickness of about 2 to 20 μm and annealing it,thereby softening it. As a result, the height difference between theprojections and depressions on the surface of the flattening layer 303falls within about 0.5 μm. BCB, which is fluidized when heated, ispreferably used as the flattening layer 303 since it is effective inflattening the surface. Alternatively, an inorganic insulating layer isformed and polished to obtain the flat layer.

Furthermore, as shown in FIG. 15, a photoresist is applied on theinterlayer insulating layer 302 and the flattening layer 303. Theresultant structure is exposed to light and developed to obtain a mask,and thereafter, subjected to etching. In this manner, contact portions201 are formed on the signal line 104 and the scanning line 105.

Then, a TFT formed on the intermediate transfer substrate 701 istransferred to the final transfer substrate 301 having wiring formedthereon. The transfer step will be explained with reference to FIGS. 16to 19. Note that a detailed structure of the TFT 102 is omitted in FIGS.16 to 19.

First, as shown in FIG. 16, an acrylic resin adhesion layer 1501 foradhering an element is formed on the flattening layer 303 of the finaltransfer substrate 301 having wiring thereon, in a thickness of about0.1 to 1 μm in accordance with screen printing. After the intermediatetransfer substrate 701 is aligned with the adhesion layer 1501, the TFT102 to be transferred and the adhesion layer 1501 are adhered to eachother. Thereafter, light is selectively applied onto the upper portionof the TFT 102 through the intermediate transfer substrate 701. In thismanner, the light absorber 702 is heated. Since the adhesiveness of theadhesion/exfoliation layer 703 is lowered by heat application, the TFT102 is separated from the intermediate transfer substrate 701 andadhered onto the final transfer substrate 301. In this light irradiationmethod, light may be applied onto the entire surface of the substrate,while the TFT 102 to be not transferred on the intermediate transfersubstrate 701 is covered with an appropriate light-shield mask 1502(indicated by a broken line in FIG. 15) in such a way that the TFT 102is not irradiated. Alternatively, a projecting portion may be formedunder the adhesion layer 1501 as a support.

Although the light absorber 702 is used herein, a thin film heatingelement made of a metal such as Ta having a large resistivity may beused in place of the light absorber 702. The thin film heating elementproduces heat by application of voltage. In this case, the thin filmheating elements arranged in a matrix are selectively heated in units.It is therefore possible to exclusively heat the TFT 102 to betransferred. Alternatively, in place of the material forming theadhesion/exfoliation layer 703 whose adhesiveness decreases by heatapplication, use may be made of a material which gains adhesiveness byheat application and loses adhesiveness by UV irradiation. Morespecifically, an alkaline series adhesive agent includingultraviolet-degradable benzophenone may be used. In this case, theultraviolet ray may be selectively applied to the TFT 102 to betransferred. Alternatively, the ultraviolet ray may be applied to thesubstrate with a mask pattern formed thereon which has an openingcorresponding to the size of the TFT 102.

As shown in FIG. 17, the TFTs 102 are transferred repeatedly, with theresult that a plurality of TFTs 102 are adhered at predeterminedpositions. An additional step of applying heat or ultraviolet rays maybe provided for securely adhering the TFTs.

Subsequently, as shown in FIG. 18, the protective layer 601 is removedby using a resist removing liquid. The removing step of the protectivelayer 601 may be set once after all TFTs 102 are transferred or may berepeated every after a single TFT is transferred.

Thereafter, an ITO film is deposited on the entire surface of the finaltransfer substrate 301 by sputtering and a photoresist is applied andthen patterned. In this manner, a connecting electrode 203 is formed forconnecting the signal line 104 to the TFT 102, as shown in FIG. 19.Simultaneously, the pixel electrode 103 is formed. In the stepsmentioned above, the active matrix substrate 101 for use in a liquidcrystal display device is completed.

In the first embodiment, the elements (TFTS) formed on the elementformation substrate 401 or the intermediate transfer substrate 701differs in density from those formed on the final transfer substrate301. Then, we will explain how to transfer the TFTS 102 when theelements formed on the intermediate transfer substrate differs indensity from those formed on the final transfer substrate, withreference to FIGS. 20A to 24B. Note that a detailed structure of the TFT102 is omitted in these figures.

A plurality of TFTs 102 regularly arranged on the element formationsubstrate 401 are transferred to the intermediate transfer substrate701, as shown in FIG. 20A. The TFTs 102 are arranged on the elementformation substrate 401 with a larger density than on the final transfersubstrate 301. The TFTs 102 are arranged on the element formationsubstrate 401 at arrangement intervals (pitches) each being an integralmultiple of the interval (pitch) of the TFTs 102 on the final transfersubstrate 301, in both row and column directions. This method isadvantageous in productivity since the density of elements formed on theelement formation substrate is increased and a plurality of TFTs 102 aretransferred. In this embodiment, the case is explained where theinterval (pitch) of TFTs on the final transfer is twice as large as thaton the element formation substrate (that is, arranged with a ¼ density).

The TFTs 102 transferred to the intermediate transfer substrate 701 areselectively transferred to the final transfer substrate 301 having thesignal lines 104 and the scanning lines 105 formed thereon, as shown inFIG. 20B.

More specifically, as shown in FIGS. 21A and 21B, TFTs 102 aretransferred to the predetermined four regions of the final transfersubstrate 301 by a first transfer operation. Since TFTS 102 are formedon the intermediate transfer substrate 701 with the density which is4-fold as high as that of the final transfer substrate 301, TFTs 102 onthe intermediate transfer substrate 701 are alternately selected andtransferred to the final transfer substrate 301.

After the first transfer, as shown in FIGS. 22A, 22B, 23A, 23B, 24A and24B, the intermediate transfer substrate 701 is shifted and another 4TFT element group alternately arranged are transferred. This procedureis repeated.

By virtue of this transfer method, the element formation substrate 401can be formed in a smaller size than the final transfer substrate 301.For example, in a HDTV having a diagonal length of 52 inches, pixels arearranged at intervals (pitches) of about 200 μm in the row direction andabout 600 μm in the column direction. In this case, if the TFTs 102 arearranged at 100 μm intervals (pitches) in both the row and columndirections, the size of the element formation substrate 401 may be{fraction (1/12)} of the final transfer substrate 301. If the elementformation substrate 401 (650 mm×650 mm) is used, it is possible to formTFTs corresponding to 4 HDTV screens of 52-inch diagonal length.

In the aforementioned embodiment, 4 TFTs are selected alternatelywithout exception. However, if necessary, a unit of two adjacent TFTsmay be alternately selected.

Above the active matrix substrate 101 thus obtained, an opposing glasssubstrate 2403 is arranged and fixed at an appropriate interval (cellgap) of about 2-6 μm from the substrate 101. The opposing glasssubstrate 2403 has a color filter 2401 and an opposing electrode 2402formed thereon. Subsequently, the cell gap is filled with liquid crystal2404 to form a liquid crystal device.

In the liquid crystal display device, 16 TFTs 102 as shown in FIG. 20Aare transferred alternately. All 16 TFTs can be transferred by fourtransfer operations. Since alignment is performed only four times, ahigh productivity is resulted. Since a plurality of TFTS 102 can besimultaneously transferred, all TFTs 1102 can be transferred in fewertimes, as described in the above. Therefore, the productivity isimproved. Moreover, the TFTs are arranged uniformly, so that the yieldis improved.

Furthermore, since TFTs 102 are formed on the element formationsubstrate 401 by using a conventional assembly line, the investment costcan be reduced. Moreover, the short circuit between wiring elements orlayers can be repaired before the TFTs are transferred on the finaltransfer substrate. It is therefore possible to obtain a highproductivity. In addition, it is possible to avoid installation of adefective TFT 102. For example, the TFT 102 formed on the elementformation substrate 401 can be checked for defect by an array tester orthe like. Therefore, transfer of the defective TFT is prevented. Inplace of the defective TFT not transferred, a non-defective TFT istransferred later.

Since each TFT 102 is formed on the separated undercoat layer 305 perTFT, no distortion occurs in an underpart layer, such as the gateelectrode, gate insulating layer or amorphous silicon layer, of the TFT102. As a result, reliability is improved. If the distortion isprevented, properties of TFT will not be changed. Moreover, exfoliationwill not occur at the time the TFTS are transferred. Therefore, adhesionreliability can be improved.

Furthermore, according to the first embodiment, it is possible tocombine the TFT manufactured accurately and the wiring manufactured lessaccurately on a large substrate. More specifically, TFT of severalhundreds of μm in dimension having the gate insulating layer 307 ofabout several hundreds of nm in thickness can be combined with thesubstrate having the wiring of 30 μm in width. Therefore, a large-screendisplay can be obtained at a low cost.

Note that the unit to be transferred is not limited only to the TFT 102,but a circuit constituted of a plurality of transistors can betransferred. If a selecting transistor and a driving transistorcontrolled by the selecting transistor in a pixel can be transferred byusing this technique, the resultant product can be used as a drivingunit for liquid crystal and EL.

Second Embodiment

In the second embodiment, a plurality of circuit units each having notonly an element but also wiring and a pixel electrode formed thereoverare formed on the element formation substrate. The circuit units aredivided and transferred a plurality of times. In this manner, a singleactive matrix substrate 101 is formed. Now, we will explained a methodfor forming the active matrix substrate 101 according to the secondembodiment with reference to FIGS. 26 to 31. In these figures, adetailed structure of the circuit unit including TFTs is omitted. Notethat like reference numerals are used to designate like structuralelements corresponding to those in the first embodiment. Overlapexplanation is omitted.

As shown in FIG. 26, an etching stopper layer 402 and, an undercoatlayer 305 are stacked on an element formation substrate 401 made ofglass. Then, a circuit unit 2501 is formed of TFTs, signal lines,scanning lines, pixel electrodes, and etc. Individual layers of thesecond embodiment are formed in the same manner as in the firstembodiment. Subsequently, a protective film 601 is formed so as to coverthe entire circuit unit 2501. The etching stopper layer 402 and theundercoat layer 305 are etched in the same size as of the protectivefilm 601. The protective film 601 is processed by photolithography witha dimensional accuracy of about 1-20 μm.

Subsequently, as shown in FIG. 27, the protective film 601 of theelement formation substrate 401 is adhered to the intermediate transfersubstrate 701 on which the adhesion/exfoliation layer 703 is formed inthe same manner as in the first embodiment. Thereafter, as shown in FIG.28, the element formation substrate 401 is etched away.

Next, as shown in FIG. 29, the circuit unit 2501 is positioned at apredetermined place of the final transfer substrate 301 having theadhesion layer 1501 formed thereon. The adhesion/exfoliation layer 703is heated through the intermediate transfer substrate 701 to reduce theadhesiveness. In this manner, the circuit element 2501 is transferred tothe substrate 301. The protective film 601 may be removed by using aresist removing liquid either after a first transfer operation or aftera second transfer operation at which all elements and wiring aretransferred, as shown in FIG. 30. In the manner mentioned above, theactive matrix substrate 101 is formed, as shown in FIG. 31.

In the case where a single large active matrix substrate 101 is formedby transferring two circuits having elements and wiring formed thereonas is in the second embodiment, how accurately the circuits are bondedis a matter of primary concern.

FIG. 32 explains a method of forming the final transfer substrate 301 bytransferring two element formation substrates 401 having elements andwiring formed thereon. FIG. 33 is a cross sectional view taken along theline 33—33 of FIG. 32. Note that a detailed structure of the TFT 102 isomitted in the FIGS. 32 and 33. As shown in FIG. 33, when the finaltransfer substrate 301 is formed by combining the element formationsubstrates 401, the interval Lg between a signal line 104 and a pixelelectrode 103 within the same element formation substrate 401 can be setequal (about 8-15 μm) to the interval Lg2 between the pixel electrode103 and a signal line 104 of another element formation substrate 401boned thereto. This technique can be applied to form a high definitionpixel for use in an HDTV. Bright images can be displayed in a largescreen having a high aperture ratio. Since the pixels and the signallines are arranged in the same manner as in a conventional active matrixsubstrate formed on the basis of a single substrate, high quality imagescan be obtained without a change of a pixel voltage caused by capacitivecoupling, at the butt-joined portion of the active matrix substrates101.

FIG. 34 shows the same transfer method as in FIG. 32. To enlarge themargin of the joint portion between the adjacent element formationsubstrates 401, the element formation substrates 401 are arrangedlinearly symmetric. FIG. 35 is a cross-sectional view taken along theline 35—35 of FIG. 34. Note that a detailed structure of the TFT 102 isomitted in FIGS. 34 and 35.

In this case, it is preferable that the interval Lp1 between the pixelelectrodes 103 in one element formation substrate 401 is equal to theinterval Lp2 between the pixel electrodes 103 at a butt-joined portionwhere the element formation substrate 401 is bonded to another one.Assuming that the width of the signal line 104 is about 30 μm and theinterval between the pixel electrode 103 and the signal line 104 isabout 5 μm, the substrates are easily butt-jointed by settingLp1=Lp2=about 40 μm.

Since no wiring is formed at the butt-jointed portion of the activematrix substrates 101, the capacitive coupling between the wiring andthe pixel electrode 103 differs from those of other portions. Therefore,if necessary, supplemental signals may be provided to the butt-joinedportion.

In the second embodiment, a large active matrix substrate 101 isprepared in one piece, without joining two substrates. Therefore, thiscase is free from the following problems: the butt-joined portion of thetwo substrates becomes thicker and elements and wiring are formed atdifferent heights between two substrates, with the result that theelements and wiring come in touch with the opposing substrate.

A glass substrate is used as the final transfer substrate 301, in thesecond embodiment. However, use may be made of a plastic substrate,resin film, ceramic substrate, thin metal-film substrate, or the like.Conventionally, it is difficult to manufacture a high definition pixelaccurately by use of the plastic substrate or the resin film. This isbecause they have a large thermal distortion and thermal expansioncoefficient. However, in the method of the present invention, it ispossible to form the elements (circuit unit) on the element formationsubstrate 401 with the same accuracy as in the case where the elementsare formed on the conventionally-used glass substrate. Since theaccurately formed elements are just transferred to the final transfersubstrate, it is possible to form a high definition image of 200 ppi onthe plastic substrate or the resin film.

Third Embodiment

In the first embodiment, after all wirings are formed on the finaltransfer substrate, the TFTs 102 transferred to the intermediatetransfer substrate are further transferred to the final transfersubstrate. However, in the third embodiment, after the TFTs aretransferred to the final transfer substrate, an interlayer insulatingfilm and then the wiring is formed on the final transfer substrate. Likereference numerals are used to designate like structural elementscorresponding to those of the first embodiment, and overlap explanationis omitted.

FIG. 36 is a schematic sectional view showing the TFT102 transferred tothe final transfer substrate 301 and wirings (scanning line, signalline) formed on the final transfer substrate 301. FIG. 37 is a schematicplan view of a single pixel at a corner portion of the active matrixsubstrate. FIG. 36 is a cross sectional view taken along the line 36—36of FIG. 37. Now, the method of manufacturing the pixel will be explainedsubsequently from the beginning.

First, the TFT 102 is formed on the element formation substrate 401 inthe same manner as in FIGS. 6 to 10 of the first embodiment. The TFT 102thus formed is transferred to the intermediate transfer substrate 701and then transferred to the final transfer substrate 301 on which wiring(scanning line) 105 is made of conductive resin, metal and the like. Thewiring 105 may be formed after the TFT 102 is transferred.

Subsequently, an interlayer insulating layer 3001 of a photosensitiveacrylic resin is formed so as to cover the TFT 102 and the wiring 105.It is not necessary to form the interlayer insulating layer 3001 byusing an organic resin such as an acrylic resin. The interlayerinsulating layer 3001 may be formed of an inorganic insulating materialsuch as SiO₂.

Next, a contact hole for connecting to an upper wiring is formed in theabove portion of the TFT 102 and in the interlayer insulating layer 3001on the wiring 105. When the interlayer insulating layer is made of aphotosensitive acrylic resin, a contact hole can be formed by exposingthe resin itself to light. However, when the interlayer insulating layeris made of SiO₂, the contact hole may be formed by applying a resist andthen subjecting to a conventionally-performed lithographic step.

Next, a pixel electrode 103 is formed on the interlayer insulating layerby ITO. Then, the pixel electrode 103 is connected to one of thesource/drain electrodes of the TFT by the signal line 104. Furthermore,the scanning line 105 and the gate electrode (not shown) of the TFT 102are connected by the connecting electrode 203 (the connecting site isnot shown). The signal line 104 and the connecting electrode 203 areformed of the same material (e.g., a conductive resin) as used in thescanning line 105.

The scanning line 105 and the TFT 102 on the final transfer substrate301 are covered with the interlayer insulating layer 3001. Since theyare covered with the interlayer insulating film 3001, breakage of thesignal line 104 is prevented even if the adhesion layer 304 extends offfrom the edge of the TFT 102 or the adhesion layer slightly curls up. Asa result, the yield is improved. The interlayer insulating layer 3001can also serve as the passivation layer of TFT 102.

The later steps are performed in the same manner as in the firstembodiment. As a result, the active matrix substrate similar to that ofFIG. 25 is completed.

As a modified example of the third embodiment, the scanning line 105 maybe formed on the interlayer insulating layer 3001. Furthermore, anotherinterlayer insulating film 3002 is formed and a signal line 104 may beformed on the interlayer insulating film 3002. Alternatively, as shownin FIG. 38, after the signal line 104 is formed on the interlayerinsulating film 3601, the interlayer insulating layer 3002 is formed,and the pixel electrode 103 may be formed on the interlayer insulatinglayer 3002 so as to overlap with the TFT 102. As described in theforegoing, it is possible to realize a display device having a largeaperture ratio by overlapping the TFT 102 and the pixel electrode, asshown in FIG. 39.

Note that a plurality of elements may be selectively transferred on thefinal transfer substrate in the third embodiment, as explained in thefirst embodiment with reference to FIGS. 20A to 24B.

Fourth Embodiment

In the fourth embodiment, a three-layer micro capsule reflective LCD isformed by use of the circuit-unit transfer technique explained in thesecond embodiment. FIG. 40 is a cross-sectional view showing the statethat a single pixel of the liquid crystal display according to thefourth embodiment is formed on the element formation substrate 401. Likereference numerals are used to designate like structural elementscorresponding to those of the first and second embodiments and overlapexplanation is omitted.

First, the etching stopper 402 and the undercoating layer 305 are formedon the element formation substrate 401 in the same manner as in thefirst embodiment. After the gate electrode 306 of the TFT 102 is formedon the undercoat layer 305, a gate insulating layer 307 is formed.

After a semiconductor layer 308, a channel protecting insulating layer309, source/drain electrodes 310 are formed on the gate insulating layer307 in the same manner as in the first embodiment, an interlayerinsulating layer 313 is formed so as to cover the TFT 102. Theinterlayer insulating layer 313 is preferably flattened. A contact holeis formed in the interlayer insulating layer 313 in which one of thesource/drain electrodes 310 is exposed. The first pixel electrode 103 ais formed on the interlayer insulating layer 313 including the contacthole. The first pixel electrode 103 a is connected to the one of thesource/drain electrodes 310 exposed in the contact hole. The first pixelelectrode 103 a is a diffuse reflection electrode which is formed bysputtering a well-reflective Al, Ag alloy or the like. To impart gooddispersion properties to the reflected light, it may be better to formuneven spots in the surface of the underlying interlayer insulatinglayer 313. This is because the metal surface of the first pixelelectrode 103 a formed thereon is formed unevenly in accordance with theuneven spots.

A spacer 3101 made of a photosensitive resin is formed at a portion nextto the first pixel electrode on the interlayer insulating layer 313 byuse of printing and photolithographic techniques. Furthermore, a metallayer of Al, Mo, Cr or the like is formed over the entire surface bysputtering. Photolithography is performed to selectively leave the metallayer on a side surface of the spacer 3101. In this way, a verticallyextended intermediate connecting electrode 3102 is formed. To theresultant structure, liquid crystal capsules 3103 a having a liquidcrystal material and a pigment filled in a transparent capsule anddispersed in a solvent are printed and then dried. The capsule layer3103 a is reduced in thickness by drying. A liquid crystal layer of afirst color is thus formed.

Then, a second pixel electrode 103 b is formed by printing a transparentresin having ITO dispersed therein on the liquid crystal layer of thefirst color and connected to one of a second TFT source and drain (notshown) by an intermediate connecting electrode (not shown). On theresultant structure, a liquid crystal microcapsule layer 3103 b of asecond color is formed in the same manner as in the liquid crystal layerof the first color. On the second liquid crystal capsule layer 3103 b, athird pixel electrode 103 c is formed in the same manner as a secondpixel electrode 103 b. The third pixel electrode 103 c is connected toone of a third TFT source/drain layers (not shown) through theintermediate connecting electrode 3102. On the second liquid crystalcapsule 3103 b, a liquid crystal capsule layer 3103 c of a third coloris formed in the same manner as mentioned above. In this way, liquidcrystal layer consisting of three layers (three color) is formed.

On the liquid crystal layer of three layers, an opposite electrode 3104of ITO is formed. Further on the opposite electrode 3104, an oppositesubstrate 3105 is formed by use of a TES film, PET film or the like.

The opposite substrate 3105 of the resultant structure is adhered to theintermediate transfer substrate 701 having an adhesion/exfoliation layer703 formed thereon, in the same manner in the second embodiment as shownin FIG. 27. Thereafter, the element formation substrate 401 is etchedaway in the same manner in the second embodiment as shown in FIG. 28.

The resultant structure of the etching stopper 402 is transferred to afilm-state final transfer substrate 301, with the water-soluble adhesionlayer 1501 interposed between them, as shown in FIG. 41. FIG. 41 showsonly a single pixel. A plurality of pixels are simultaneouslytransferred to a large substrate (final substrate) in the same manner asin the second embodiment. If the transfer operation is repeated aplurality of times, it is possible to achieve a liquid crystal displaydevice having pixels arranged in a matrix form. However, the transferoperation may be done only once.

According to the fourth embodiment, after the second and third pixelelectrodes and the vertically-extended intermediate electrode whichconnects the second and third pixel electrodes to the correspondingTFTs, are formed accurately, they are transferred onto the film-formfinal transfer substrate. It is therefore possible to realize a highdefinition pixel of about 200 ppi. The stacked liquid crystal structureis indispensable to obtain a bright reflection image with a goodcolor-reproductivity in the reflective LCD.

According to the present invention, it is possible to manufacture anactive matrix substrate providing a high definition image at a low costeven if a large substrate or a non-glass material is used.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A method of manufacturing an active matrixsubstrate comprising: a first step of forming a plurality of elements ona first substrate; a second step of forming wirings on a secondsubstrate; a third step of transferring some elements selected from saidplurality of elements onto said second substrate from said firstsubstrate; and a fourth step of selectively connecting said someelements transferred onto said second substrate to said wirings, whereinsaid third step includes the steps of: forming an adhesion layer on athird substrate; transferring said plurality of elements formed on saidfirst substrate to said third substrate by said adhesion layer; formingadhesion thick film pads at portions on said second substrate, saidadhesion pads corresponding to said selected elements selectivelytransferred to said second substrate; and bonding said selected elementson said third substrate to said adhesion thick film pads, while otherunselected elements on said third substrate are left spaced apart fromsaid second substrate during said bonding step.
 2. The method ofmanufacturing an active matrix substrate according to claim 1, whereinsaid step of transferring said plurality of elements formed on saidfirst substrate to said third substrate by said adhesion layer includesthe steps of: bonding said plurality of elements formed on said firstsubstrate to said third substrate by said adhesion layer; and etchingaway said first substrate.
 3. The method of manufacturing an activematrix substrate according to claim 1, wherein said third step includesa step of selecting said some elements such that a largest interval oftwo adjacent elements arbitrarily chosen from said some elements islarger than a largest interval of two adjacent elements arbitrarilychosen from said plurality of elements formed on said first substrate.4. The method of manufacturing an active matrix substrate according toclaim 1, wherein said third step includes a step of selecting said someelements at predetermined intervals thereamong, and a step of repeatingsaid step of selecting said some elements.
 5. The method ofmanufacturing an active matrix substrate according to claim 1, whereinsaid third step further includes a step of peeling off said someelements by heating said adhesion layer.
 6. The method of manufacturingan active matrix substrate according to claim 5, wherein said third stepfurther includes the steps of: forming a plurality of light absorbers onportions of said third substrate, which corresponds to portions on whichsaid plurality of elements are to be bonded by said adhesion layer, andselectively heating portions of said adhesion layer by irradiating lightto some light absorbers of said plurality of light absorberscorrespondingly provided to said some elements to be transferred forpeeling off said some elements.
 7. The method of manufacturing an activematrix substrate according to claim 5, wherein said third step furtherincludes the steps of: forming a plurality of heating members onportions of said third substrate, which corresponds to portions on whichsaid plurality of elements are to be bonded by said adhesion layer,before the step of forming said adhesion layer, and selectively heatingportions of said adhesion layer by some heating members of saidplurality of heating members correspondingly provided to said someelements to be transferred for peeling off said some elements.
 8. Themethod of manufacturing an active matrix substrate according to claim 1,wherein said first step includes the steps of: forming an underlyinglayer on said first substrate, said underlying layer including anetching stopper layer formed on said first substrate and an undercoatlayer formed on said etching stopper layer; forming said plurality ofelements on said underlying layer; and forming a protective layerindividually on each of said plurality of elements, such that saidplurality of elements are covered with said underlying layer and saidprotective layer.
 9. The method of manufacturing an active matrixsubstrate according to claim 8, further comprising a step of separatingsaid underlying layer including said etching stopper layer and saidundercoat layer into sections such that said underlying layer remainsonly just under each of said plurality of elements.
 10. The method ofmanufacturing an active matrix substrate according to claim 8, whereinsaid fourth step includes etching away said protective layer prior toconnecting said some elements to said wirings.
 11. A method ofmanufacturing an active matrix substrate comprising: a first step offorming a plurality of elements on a first substrate; a second step oftransferring some elements selected from said plurality of elements ontoa second substrate from said first substrate; a third step of formingwirings on said second substrate after said second step; and a fourthstep of selectively connecting said some elements and said wirings,wherein said second step includes the steps of: forming an adhesionlayer on a third substrate; transferring a plurality of elements formedon said first substrate onto said third substrate by said adhesionlayer; forming adhesion thick film pads at portions on said secondsubstrate, said adhesion thick film pads corresponding to said selectedelements selectively transferred to said second substrate; and bondingsaid selected elements on said third substrate to said adhesion thickfilm pads, while other unselected elements on said third substrate areleft spaced apart from said second substrate during said bonding step.12. The method of manufacturing an active matrix substrate according toclaim 11, herein said step of transferring said plurality of elementsformed on said first substrate to said third substrate by said adhesionlayer further comprises the steps of: bonding said plurality of elementsformed on said first substrate to said third substrate by said adhesionlayer; and etching away said first substrate.
 13. The method ofmanufacturing an active matrix substrate according to claim 11, whereinsaid second step includes a step of selecting said some elements suchthat a largest interval of two adjacent elements arbitrarily chosen fromsaid some elements is larger than a largest interval of two adjacentelements arbitrarily chosen from said plurality of elements formed onsaid first substrate.
 14. The method of manufacturing an active matrixsubstrate according to claim 11, wherein said second step includes astep of selecting said some elements at predetermined intervalsthereamong, and a step of repeating said step of selecting said someelements.
 15. The method of manufacturing an active matrix substrateaccording to claim 11, wherein said second step further includes a stepof peeling off said some elements by heating said adhesion layer. 16.The method of manufacturing an active matrix substrate according toclaim 15, wherein said second step further includes the steps of:forming a plurality of light absorbers on portions of said thirdsubstrate, which corresponds to portions on which said plurality ofelements are to be bonded by said adhesion layer, and selectivelyheating portions of said adhesion layer by irradiating light to somelight absorbers of said plurality of light absorbers correspondinglyprovided to said some elements to be transferred for peeling off saidsome elements.
 17. The method of manufacturing an active matrixsubstrate according to claim 15, wherein said second step furtherincludes the steps of: forming a plurality of heating members onportions of said third substrate, which corresponds to portions on whichsaid plurality of elements are to be bonded by said adhesion layer,before the step of forming said adhesion layer, and selectively beatingportions of said adhesion layer by some heating members of saidplurality of heating members correspondingly provided to said someelements to be transferred for peeling off said some elements.
 18. Themethod of manufacturing an active matrix substrate according to claim11, wherein said first step includes the steps of: forming an underlyinglayer on said first substrate, said underlying layer including anetching stopper layer formed on said first substrate and an undercoatlayer formed on said etching stopper layer; forming said plurality ofelements on said underlying layer; and forming a protective layerindividually on each of said plurality of elements, such that saidplurality of elements are covered with said underlying layer and saidprotective layer.
 19. The method of manufacturing an active matrixsubstrate according to claim 18, further comprising a step of separatingsaid underlying layer including said etching stopper layer and saidundercoat layer into sections such that said underlying layer remainsonly just under each of said plurality of elements.
 20. The method ofmanufacturing an active matrix substrate according to claim 18, whereinsaid fourth step includes etching away said protective layer prior toconnecting said some elements to said wirings.
 21. A method ofmanufacturing an active matrix substrate comprising: a first step offorming an underlying layer on a first substrate, said underlying layerincluding an etching stopper layer formed on said first substrate and anundercoat layer formed on said etching stopper layer; a second step offorming a plurality of circuit units, on said underlying layer, composedof at least one element and at least one wiring connected to said atleast one element, followed by separating said underlying layer intosections such that said underlying layer remains only just under each ofsaid plurality of circuit units; a third step of bonding said pluralityof circuit units formed on said first substrate to a third substrate viasaid underlying layer and an adhesion layer formed on said thirdsubstrate; a fourth step of etching away said first substrate; and afifth step of selectively transferring said plurality of circuit unitsadhered onto said third substrate to a second substrate.
 22. The methodof manufacturing an active matrix substrate according to claim 21,wherein said fifth step includes a step of selectively heating portionsof said adhesion layer on which said plurality of circuit units to betransferred are formed, to thereby transfer said circuit units from saidthird substrate to said second substrate.
 23. The method ofmanufacturing an active matrix substrate according to claim 21, whereineach of said plurality of circuit units includes a plurality of pixelelectrodes, and said fifth step is repeated a plurality of times suchthat an interval between adjacent electrodes of said plurality of pixelelectrodes is kept substantially constant through repeated transfersteps of said plurality of circuit units.
 24. The method ofmanufacturing an active matrix substrate according to claim 21, whereinsaid undercoat layer includes at least a silicon nitride layer.
 25. Themethod of manufacturing an active matrix substrate according to claim21, wherein said fourth step includes etching away said first substratewith said underlying layer leaving to cover said plurality of circuitunits, and said fifth step includes transferring said plurality ofcircuit units to said second substrate by said underlying layer.
 26. Themethod of manufacturing an active matrix substrate according to claim21, wherein said second step includes a step of forming a protectivelayer individually on each of said plurality of circuit units, such thatsaid plurality of circuit units are covered with said underlying layerand said protective layer.
 27. The method of manufacturing an activematrix substrate according to claim 26, wherein said fifth step includesetching away said protective layer.